1. Field of the Invention
The present invention relates to improvements in an optically imaging method and apparatus of a reduction projection aligner or the like which projects a projected pattern of a pattern source onto an exposed material, e.g., by means of illuminating light from a light source.
2. Description of the Related Art
Heretofore, a pattern generator with a variable aperture has been generally employed for a pattern lithograrhy printing a nonrectangular pattern on an exposed material. This prior-art pattern generator provides a rectanglar pattern normally provided by two pairs of opposite blades both the pairs together constituting a variable aperture defining apparatus and stepwise and repeatedly projects the rectangular pattern through an optical lens system onto an exposed material thereby to generate an optional exposed pattern in the form of an approximate circle, an approximate triangle, square or the like.
The prior-art pattern lithography with the pattern generator entails a problem in that it requires much a printing time, since an assembly of rectangular patterns provides a predetermined exposed pattern, a single exposure operation cannot generate an optional pattern on the exposed material and dimensions of each rectangular pattern must be instructed and the exposed material must be 2-dimensionally moved to generate the optional pattern.
In order to solve the problem, the present applicant proposed a variable aperture defining apparatus which has at least one pair of two opposite blades each movable relative to the other, at least one of the two opposite blades having a V-shaped notch, so as to generate an optional polygonal pattern in Japanese Utility Model Application No. SHO 36-42799. In this case, there is yet a problem in that the variable aperture defining apparatus can generate an approximately circular pattern but cannot generate a complete circular pattern and dimensions of the polygonal patten can be stepwise changed but cannot be steplessly changed. Japanese Unexamined Application Publication No. SHO 61-220895 also discloses an optical plotter for drawing an approximate circle which draws an approximate circle by means of two pairs of blades each pair having a notch or recess. This prior-art plotter also entails such a problem as in Japanese Utility Model Application No. SHO 63-42799.
Thus, the present applicant proposed a pattern printing method and an apparatus therefor which did not mechanically change a pattern image of the variable aperture defining apparatus or the like but rather optically changed a magnification of a patten image in Japanese Patent Application No. SHO 63-24629. The teaching of this Japanese Patent Application No. SHO 63-24629 is that illuminating light from a light source is projected onto a pattern source, an optical lens system produces the resulting projected image of the pattern source on an exposed material, at least one of the pattern source and the exposed material is moved along an optical axis, or a magnification correcting lens is provided between the pattern source and optical lens system, at least one of the pattern source and magnification correcting lens being moved in the optical axis and then the patten source and magnification correcting lens being moved while maintaining moving positions thereof so that the imaging position of the magnification correcting lens conincides with a pretermined position, whereby a magnification on the exposed material of the projected pattern is steplessly changed.
In accordance with the prior-art pattern printing method and apparatus of Japanese Patent Application No. SHO 63-24629, however, there is yet a problem in that a magnification between the projected pattern of the pattern source and a similar projected pattern produced on the exposed material can be optionally changed while any of the pattern source, exposed material and magnification correcting lens must be moved along the optical axis in order to change the magnification and while since the imaging position of the projected pattern produced on the exposed material is displaced by each movement, a corresponding displacement must be compensated, so that an adjustment for changing the magnification is complicated and the resolution of the projected pattern produced on the exposed material is reduced.